The present proposed research includes three parts. The first part consists of a study of the free radical damage of cell components caused by the aerobic oxidation of bisulfite or sulfite ions. The O2 minus, OH. and SO3 minus. radicals, which are generated during the aerobic oxidation of sulfite, are particularly suspect as toxic agents which may destroy amino acids, hormones, lipids and coenzymes. The next part is to examine the in vitro effect of sulfite ion on various enzyme and membrane systems and to characterize sulfite oxidase from plant sources. Sulfite oxidase has been suspected to be the key enzyme responsible for the detoxification of S02. The third part will involve the in vivo effect of SO2 on metabolism of harvested fruits and the fate of SO2 in the fruit.